Genetic diversity study of Etheostoma percnurum species complex
Genetic diversity study of Etheostoma percnurum species complex
Jacob F. Brumley and Rebecca E. Blanton
Johansen Lab of Ichthyology at Austin Peay State University, Dept. of Biology and Center of Excellence for Field Biology
In 2008, the Etheostoma percnurum species complex was described as 4 distinct species by Rebecca E. Blanton and Robert E. Jenkins.1 The 4 species within the complex are:
Etheostoma percnurum (Jenkins 1994) found in the Clinch River system of the Tennessee River drainage.
Etheostoma marmorpinnum (Blanton & Jenkins 2008) found in the Little River system of the Tennessee River drainage.
Etheostoma sitikuense (Blanton 2008) found in the Little Tennessee River system of the Tennessee River drainage.
Etheostoma lemniscatum (Blanton 2008) found in the Big South Fork system of the Cumberland River drainage.
These 4 species were described as genetically and meristically distinct and were elevated to specis status. However, all species within the complex are federally listed as endangered under the species name Etheostoma percnurum by USFWS and the ESA of 1973.
This work is funded by USFWS to look at the genetic diversity of 3 of the species within the complex: E. percnurum, E. marmorpinnum, and E. lemniscatum.
1 Blanton, R. E., and R. E. Jenkins. 2008. Three new darter species of the Etheostoma percnurum complex (Percidae, subgenus Catonotus) from the Tennessee and Cumberland river drainages. Zootaxa 1963: 1-24.
Genetic diversity of a highly imperiled, habitat specialist, Etheostoma marmorpinnum, from Little River, TN
Figure 1. Etheostoma marmorpinnum from Little River at River John’s
Introduction
Habitat loss and fragmentation cause declines in population connectivity and abundance, which contributes to genetic drift and loss of genetic diversity.1,2,3 Decreases in abundance and genetic diversity can lead to inbreeding and genetic homogenization of the population, reducing fitness of both the individuals and the population as a whole.2,3,4,5 The federally endangered Marbled Darter, Etheostoma marmorpinnum, (Fig. 1) is found in the Little River in Tennessee. Although once known in the South Fork Holston River, the darter is now found in only a 20 rkm stretch of the lower Little River and is restricted in range both upstream and downstream by dams. Its restricted range, patchy habitat, small population size, and limited larval dispersal make this species highly susceptible to further habitat loss or degradation. Genetic monitoring protocols can establish a genetic diversity baseline and track changes in genetic diversity over time. Such temporal measures of genetic diversity can be specifically linked to changes in habitat or to management practices to determine how such changes have impacted genetic diversity.6,7 Genetic diversity of E. marmorpinnun has not been previously estimated, despite past population loss, propagation, and reintroductions.
Objectives
Estimate genetic diversity at site and species levels.
Provide a genetic baseline for conservation and future genetic monitoring.
Methods and Materials
Fin clips collected during snorkel surveys at 3 locatlities in lower Little River, spanning current range of species (Fig. 2, 3, 4)
Six variable microsatellite loci optimized for PCR amplification from a set of 20 primers produced for Etheostoma lemniscatum
R(3.5.1) used to run a standard suite of population genetic analyses to estimate genetic diversity and population structure
Figure 2. Blount County, TN.
Figure 3. Collection sites on Little River, TN. Sites 1 & 3 represent the downstream and upstream extents of the known range.
Figure 4. Satellite image of site locations.
Results
Discussion
Literature Cited
1 Farhig, L. 1997. Relative effects of habitat loss and fragmentation on population extinction. The Journal of Wildlife Management 61: 603-610.
2 Johannesson, K. and C. Andre. 2006. Life on the margin: genetic isolation and diversity loss in a peripheral marine ecosystem, the Baltic Sea. Molecular Ecology 15: 2013-2029.
3 Thrush, S. F., J. Halliday, J. E. Hewitt, and A. H. Lohrer. 2008. The effects of habitat loss, fragmentation, and community homogenization on resilience in estuaries. Ecological Applications 18: 12-21.
4 Frankham, R. 1996. Relationships of genetic variation to population size in wildlife. Conservation Biology 10: 1500-1508.
5 Reed, D. H. and R. Frankham. 2003. Correlation between fitness and genetic diversity. Conservation Biology 17: 230-237.
6 Schwartz, M. K., G. Luikart, and R. S. Waples. 2006. Genetic monitoring as a promising tool for conservation management. TRENDS in Ecology and Evolution 22: 25-33.
7 Hansen, M. M., I. Olivieri, D. M. Waller, E. E. Nielsen, and the GeM Working Group. 2012. Monitoring adaptive genetic responses to environmental change. Molecular Ecology 21: 1311-1329.
8 Frankham, R. 1995. Conservation genetics. Annual Review of Genetics 29: 305-327.
9 Morrissey, M. B., and D. T. de Kerckhove. 2009. The maintenance of genetic variation due to asymmetric gene flow in dendritic metapopulations. The American Naturalist 174: 875-889.
10 Paz-Vinas, I., G. Loot, V. M. Stevens, and S. Blanchet. 2015. Evolutionary processes driving spatial patterns of intraspecific genetic diversity in river ecosystems. Molecular Ecology 24: 4586-4604.
11 Thomaz, A. T., M. R. Christie, and L. L. Knowles. 2016. The architecture of river networks can drive the evolutionary dynamics of aquatic populations. Evolution 70: 731-739.
Acknowledgements
We thank Conservation Fisheries, Inc. (P. Rakes and C. Ruble) and N. Disotell for their extraordinary assistance in the field; USFWS for funding this project; APSU Center of Excellence for Field Biology for equipment; The home owners and River John’s for access to the Little River.